Living batteries

Conventional metal batteries are very caustic, dangerous if spilled and disposing of them poses an environmental risk. But now a team at St Louis University is developing 'living batteries' fuelled by alcohol, making them a safe, sustainable and efficient alternative.

Transcript

Robyn Williams: Professor Shelley Minteer at St Louis University in Missouri is putting alcohol into batteries for mobile phones and laptops. Why?

Shelley Minteer: Because they're far more efficient than your normal metal batteries. Metal batteries are very inefficient. Anybody who has ever used a cell phone, you know that you might purchase a battery that has a lifetime of, you know, three hours on day one, as you recharge it, the next time you only have two hours and 50 minutes, then two hours and 45 minutes et cetera. So they're not really reversible and they're very inefficient, so if we can provide efficiency...a living cell is a very efficient organism and so it efficiently oxidises the systems and then you can increase your lifetime and increases your power output.

Robyn Williams: Yes, but they're also wet and they're also fragile.

Shelley Minteer: Yes, they are also wet and they are also fragile. If you look at most traditional batteries, they are wet for all intents and purposes, so they have a gel in them, but they are gelatinous, there is a liquid that can leach out. So both systems are somewhat wet, which does cause problems in thinking about leaking. As far as the fragile aspects of things, that's definitely something that we've been working on.

Robyn Williams: And you're working on doing something, incorporating...you talk about nano-architecture; that's membranes, isn't it, like living things?

Shelley Minteer: Yes. So if you look at a cell there's a series of membranes in the cell and a lot of the enzymes are actually embedded within the membrane, so they're membrane-bound enzymes, and so what we're doing is sort of mimicking those cellular membranes within...at an electrode surface. So we're making polymer-based membranes.

Robyn Williams: And you're putting booze inside.

Shelley Minteer: Yes. So we look at a wide variety of fuels and our most popular is ethanol. Ethanol is a very simple fuel to look at, fairly easy for us to oxidise with enzymes. One of the real advantages of using enzymes is they aren't as dependant on impurities as things like metals are. So metals will be easily passivated by aldehydes and ketones that might be in wine, or by proteins, and we don't have that problem with enzymes. So with a traditional battery you have to use a very pure fuel but we can get away with using beer or wine or gin. We have some problems with red wine; the enzymes don't like red wine, but the white wine, gin and beer work quite well.

Robyn Williams: Before I agonise about the waste of good drinking, nonetheless, you would use standard ethanol, which of course you can get from growing crops and biofuels.

Shelley Minteer: Yes. I'm originally from the mid-west, I grew up in a small farming community, so our original effort has not been to actually put some type of drinking alcohol in the fuel cell, but instead use alcohol from crops, from fermentation of corn. One of the advantages, though, in not being so dependant on purity is they go through extreme measures within the corn alcohol industry in order to get a very pure sample, and for the fuel cell application we don't need as pure a sample. So it cuts down their manufacturing cost at the co-op.

Robyn Williams: Much cheaper. But if you had one of your batteries on your desk or you handed it to me, what would it look like?

Shelley Minteer: Somewhat like a traditional battery except that they have to have air holes because they breathe oxygen, so they oxidise the fuel and they reduce oxygen. So they really have two components that you wouldn't normally see in a battery; one is air holes to allow oxygen to get through, and the other is a fuel cartridge to allow fuel to be added to the system.

Robyn Williams: So you'd add a bit of booze now and then, but how long would it last?

Shelley Minteer: A typical pen cap full of alcohol would last about 30 days.

Robyn Williams: And the battery itself would go on forever?

Shelley Minteer: At this point we have lifetimes on the order of two years.

Robyn Williams: That's pretty good, isn't it?

Shelley Minteer: Yeah, that's pretty good. So we started out with lifetimes of a couple of months and we've been improving the membranes to the point where we now have active lifetimes in the 24 to 26 month range.

Robyn Williams: And the output would be steady, would it? I know that some batteries vary anyway, but you'd get a steady supply so that you could run almost any equipment.

Shelley Minteer: All batteries are dependant on temperature, so if you've ever tried to start your car when it's quite cold...they're all dependant on temperature, so these type of bio-fuel cells are just as dependent...or bio-batteries are just as dependant on temperature as any other battery would be, and they are dependant on having fuel. So as you get to the end of your fuel cartridge you will start to see a decay in power. So if you're not actively replacing your fuel cartridge, you'll see a steady decrease down to no current.

Robyn Williams: When do I buy one? Is it available?

Shelley Minteer: It's not available, we're still in the R and D range...two to three years is sort of our ballpark lifetime that we've been aiming for, mainly because most of your small electronics. People buy a two-year cell phone contract in the US, so people are maintaining a battery and expecting a laptop or a cell phone battery to last two to three years. So we've been working on lifetime very dramatically, and at this point we're starting to go from lifetime studies into prototyping studies so that we can build prototypes to fit in my cell phone so I can have them sitting on my desk.

Robyn Williams: So not only fitting in a cell, but would it sit in my electric car?

Shelley Minteer: You know, lots of people ask me that question, whether or not we're looking at large-scale applications. At this point we're looking at small-scale applications for one reason, not because the technology can't be used for a car but because there's a lot less engineering in small electronics than there is in your car. Cars are very complex and so we're starting with something that is relatively easy where we have a passive fuel that's in there and we just change a cartridge, rather than having to maintain fuel injectors et cetera. So cars are definitely more complex and what I consider a long-term application not a short-term application.

Robyn Williams: I was told by somebody at the UCLA who worked on hydrogen, he said that the revolution is going to be caused not by car people opting for hydrogen but by, as you were saying, cell phones and laptop people using these more cunning technologies, and through that the revolution will automatically happen in transport because of the push in this enormous market in cell phones and laptops. Do you agree?

Shelley Minteer: Yes, I definitely agree. It's one of those things where people need to get accustomed to something, and they very readily change electronics, you know, the new gadget comes out and you've got to have the new gadget. So we are very open to making changes in portable electronics. And so we're not so open in the concept of getting rid of the combustion engine, so there definitely will have to be a transition of people getting comfortable with the technology, with their small electronics, so that they they'll buy and try it there, and then build a market on it.

Robyn Williams: Will it be revolutionary, both in a technological sense and a green sense?

Shelley Minteer: Yes. One of the huge problems with the idea of us going from combustion engines to, say, batteries or our hybrid cars is that batteries still have these heavy metals and there is definitely an environmental issue associated with disposal of any batteries. As we go into traditional fuel cells then we're replacing those toxic metals with precious metals...so things like platinum, which become less of a problem in terms of the environment, become more of a problem in terms of we only have so much platinum on Earth. Then as we move out of the traditional fuel cell into the bio-fuel cell, you're starting to get into a different situation where now you have a completely renewable resource. So we're using an enzyme, which is a renewable resource and we can grow more of it, and it is environmentally friendly so it will completely biodegrade and we don't have those kind of environmental issues.